Equilibrium Adsorption Isotherms Research Articles

Effect of Adsorption Deacidification on the Quality of Peony Seed Oil.

To overcome the issues in the traditional deacidification processes of peony seed oil (PSO), such as losses of neutral oil and trace nutrients, waste discharge, and high energy consumption, adsorption deacidification was developed. The acid removal capacity of adsorbent-alkali microcrystalline cellulose was evaluated using the isothermal adsorption equilibrium and the pseudo-first-order rate equation. The optimized adsorption deacidification conditions included adsorbent-alkali microcrystalline cellulose at 3%, a heating temperature of 50 °C, and a holding time of 60 min. The physicochemical, bioactive properties, antioxidant capacities, and oxidative stabilities of PSO processed by alkali refining and oil-hexane miscella deacidification were compared under the same operating conditions. Fatty acid content was not significantly different across all three methods. The deacidification rates were 88.29%, 98.11%, and 97.76%, respectively, for adsorption deacidification, alkali refining, and oil-hexane miscella deacidification. Among the three deacidification samples, adsorption deacidification showed the highest retention of tocopherols (92.66%), phytosterols (91.96%), and polyphenols (70.64%). Additionally, the obtained extract preserved about 67.32% of the total antioxidant activity. The oil stability index was increased 1.35 times by adsorption deacidification. Overall, adsorption deacidification can be considered a promising extraction technology in terms of quality as compared to alkali refining and oil-hexane miscella deacidification.

Efficient removal of fluoride on aluminum modified activated carbon: an adsorption behavioral study and application to remediation of ground water

In recent times, ground water contamination by toxic elements is of great concern and it is to be addressed for consumption of human, animal, and plant growth. In this context, we have synthesized an adsorbent by modifying commercially available activated carbon with aluminum and tested for de-fluoridation studies. The activity results suggested that the optimized adsorbent is highly efficient in removing the fluoride from ground water. Adsorption maxima are obtained over a wide pH range from 4 to 9, with a contact time of 15 minutes at a dosage of 4 g/L. The results also revealed that the synthesized adsorbent is suitable for application in ground water without any pH adjustment and has exhibited 85%–95% tolerance for common anions in the range of 100–500 mg/L. Equilibrium adsorption isotherm models as well as kinetics of adsorption were applied for the system. An adsorption capacity of 20.4 mg/g and fast kinetics observed are most favorable for defluoridation. Reuse of adsorbent over repeated cycles was investigated. Residual amount of aluminum in treated water is found to be negligible. The removal of toxic elements like Pb, Cd, Cr, Cu, Ni, Zn, As, and Se under the optimized experimental conditions has also been investigated. Al-AC found to be a highly promising material for removal of fluoride and toxic metals from drinking water.

Perspectives on Adsorption. What else? A personal view

In this Perspectives paper I reviewed my work on the adsorption area starting with section 1- Looking back…and the reading of the old book of C.L. Mantell in 1969 and my doctoral work in Nancy where I learned fixed-bed processes and mechanistic models. Then I mention the creation of my research group at the U. Porto and the organization of four NATO Advanced Study Institute bringing top researchers in the area as well as the origin of the International Adsorption Society and the Fundamentals of Adsorption conferences. In Section 2, I focus on lessons learned mentioning what is important to understand batch isothermal adsorption (adsorption equilibrium isotherm, operating line, LDF kinetic model) and fixed-bed processes, namely the concept of compressive and dispersive concentration waves resulting from De Vault equation (1943). Going from batch to continuous processes is illustrated with the case of Simulated Moving Bed (SMB) technology. In Section 3 I suggest a roadmap for the development of adsorption processes and sorption-enhanced reaction processes (SERP) combining experiments and process simulation, with reference to the importance of IAST theory in predicting multicomponent adsorption equilibrium, shaping and 3D printing of materials and the contribution of molecular simulation both for the screening of adsorbents and prediction of adsorption isotherms and transport properties. Finally in section 4, I discuss some challenges and opportunities related with difficult separations and the relevant choice of materials and processes together. I believe that in this time of transition from fossil energy to renewables many existing technologies will find a place in future biorefineries. Some references are made to CCUS and Power to Gas processes as an example of SERP. Finally, I address the importance in the future of hybrid modeling involving not only mechanistic aspects but incorporating data-driven modeling with tools from AI and machine learning and application of adsorption in different field as perfume engineering.

Adsorption of Melachite Green onto Activated Carbon Prepared from Clerodendrum serratum

The Clerodendrum serratum leaves obtained from nearby Nagai district, it was used as an adsorbent for the removal of malachite green dye from aqueous solution. The various factors affecting adsorption, such as initial dye concentration, contact time, adsorbent dose and initial pH of solution were evaluated on adsorption of malachite green dye on activated Clerodendrum serratum carbon. The equilibrium adsorption isotherms were analyzed by Langmuir and Freundlich equations. Both Langmuir and Freundlich models can describe the adsorption equilibrium but the Langmuir model shows better agreement. The kinetics of the adsorption process was tested by pseudo-first-order, pseudo-second order, Elovich and Intra-particle diffusion models. It was shown that adsorption of malachite green dye could be described by the pseudo-second order kinetic model. Thermodynamic parameters such as Gibbs free energy (G0 ), the enthalpy (H0 ) and the entropy change of sorption (S0 ) have also been evaluated and it has been found that the adsorption process was spontaneous, feasible and endothermic in nature. The results indicated that activated Clerodendrum serratum carbon can be used as an effective and low-cost adsorbent to remove malachite green dye from aqueous solution.

Simultaneous adsorption of ciprofloxacin drug and methyl violet dye on boron nitride nanosheets: experimental and theoretical insights.

In this study, hexagonal boron nitride (BN) with a sheet-like morphology is successfully synthesized by reacting borax (Na2B4O7·10H2O) and urea (CO(NH2)2) powders in air via a facile microwave-assisted method within a short reaction time (15 min). The as-prepared product is structurally characterized via Fourier transformation infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersion X-ray analyzer (EDX), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area measurements. The adsorption process of methyl violet (MV) as a model of organic dyes and ciprofloxacin (CIP) as a model of antibiotics onto the boron nitride nanosheets has been experimentally and theoretically studied. The BN nanosheets exhibit the maximum adsorption capacity of 320.94 mg g-1 for MV dye and 266.29 mg g-1 for CIP antibiotic. The Freundlich isotherm model was suitable to describe the adsorption equilibrium isotherm data and the pseudo second-order model reflected the adsorption kinetics well. The calculated thermodynamic parameters show that the adsorption process is spontaneous under the measured conditions. The adsorption of CIP, MV and CIP + MV molecules on the surface of BN has been investigated through DFT calculations. The charge transfer and high adsorption capacity demonstrate the potential of BN nanosheets as an adsorbent for the simultaneous removal of MV dye and CIP drug from contaminated water.

Linear and Non-Linear of 2-Parameters Adsorption Equilibrium Isotherm Models of Synthetic Arsenic Wastewaters

Contamination of groundwater and surface water with arsenic (Asic) has become emerging health and environmental problem around the world. This problem has received significant attention amongst scientists for the development of new adsorbents to remediate Asic -contaminated water. The ability of the immobilized powdered eggshell (Poes), as adsorbent, to remove Asic was studied under batch conditions. Equilibrium data were analysed using non-linear and linearized two-parameter adsorption isotherms models (Langmuir, Freundlich, Elovich, Flory–Huggins, Temkin, Frenkel- Hasley- Hill; Langmuir- Vageler, Hill-de Boer, Kiselev, Fowler- Guggenheim, Dubinin –Radushkevich, Jovanovic, Harkins–Jura and Halsey). The performance of adsorption equilibrium isotherm models was evaluated statistically using the following analysis of variance (ANOVA), model of' selection criterion (MSC), Coefficient of Determination (CD), Correlation coefficient (R) and Akaike Information Criterion (AIC). The study revealed that for non-linear equilibrium isotherm models, Freundlich (0.986 and 3.906) > Fowler—Guggenheim (0.996 and 5.176) and Hasley (0.986 and 3.906) performed well in predicting experimental data-based on the magnitudes of R and MSC. The linearized adsorption equilibrium isotherm models, Dubinin – Radushkevich (0.993 and 4.621) <Temkin (0.994 and 4.701) < Kiselev (0.9999 and 8.856). These three models are the best isotherm models for Asic adsorption onto Poes. It was concluded that Poes particles contain numerous materials that aid Asic adsorption. Based on the performance indicators and to ensure reliable results of adsorption equilibrium data analysis through the adsorption isotherm models, it is necessary that these data sets should be evaluated by both non-linear and linear regression analyses.

Fate and Transport of Lead and Copper in Calcareous Soil

Heavy metals transport to groundwater relies on the characteristics of soil, such as carbonate and clay minerals, organic matter content, soil pH, and some other factors. Most of the heavy metals in calcareous soils are precipitated as metal carbonate minerals; consequently, their transport to the groundwater is not anticipated. Therefore, the current study focused on the impacts of calcium carbonate presence on the adsorption and transport of lead (Pb) and copper (Cu) in calcareous soil using batch and column experiments. To elucidate the contaminants removal mechanisms in calcareous soils, extensive laboratory batch investigations were conducted to study the equilibrium kinetic and adsorption isotherm characteristics of the two studied heavy metals. The quick adsorption of Pb2+ and Cu2+ by soil was seen in kinetics trials. In addition, Pb2+ and Cu2+ sorption onto the soil was best described by the pseudo-second order kinetic model (R2 = 0.9979 and 0.9995 for Cu2+ and Pb2+, respectively). To explain the equilibrium sorption data, the Freundlich isotherm showed the best fitness to Pb2+ (R2 = 0.96) and Cu2+ (R2 = 0.98), collectively. The Freundlich parameters revealed that the Pb2+ has favorable adsorption; however, Cu2+ has unfavorable adsorption onto the soil. The results of column experiments showed the higher binding of Pb2+ than Cu2+ to the top surface of the soil column, making the movement of these two metals very slow. In columns, most of the Pb2+ and Cu2+ ions were sorbed at an initial 5 and 10 cm, respectively. The findings of this study will help in understanding the fate of heavy metals in calcareous soils.

Biosorption of Congo Red dye from aqueous solutions using pristine biochar and ZnO biochar from green pea peels

To minimize the catastrophic influence of contaminated water, smart technology-based wastewater treatment processes are mandatory for safe water and sanitation. Nanometric metal oxides supported with biochar are green choices for futuristic adsorbents for water decontamination with versatility, simplicity, high surface reactivity, and efficacy. In this study, reactive Congo Red (CR) from an aqueous solution was decontaminated using prepared innovative green pea peels biochar (GPBC), and zinc oxide green pea peels biochar nanocomposite (ZnO/GPBC). The characterizations of GPBC and ZnO/GPBC were performed by EDX, TEM, XRD, BET, FTIR, and point of zero charge. The role of experimental conditions of initial concentration (50–250 mg/l), GPBC and ZnO/GPBC dosage pH (2−12), temperature (20–60 oC) and interaction time (0–90 min) were examined. The results revealed that ZnO/GPBC demonstrated better performance for anionic CR dye removal that recorded as 98% compared to 90% using GPPBC under optimized environment conditions. The examination of adsorption equilibrium isotherm displayed the validity of Freundlich and Langmuir model for description the dye decolorization onto ZnO/GPBC and GPBC, respectively, as best fitted models. Moreover, the kinetics studies disclosed pseudo-second-order (PSO) for both studied materials. The monolayer sorption capacities were 114.94 mg/g for ZnO/GPBC and 62.11 mg/g for GPBC, both exhibiting competitive performances with other carbon-based adsorbents available in the literature. The thermodynamic studies disclosed favorable, spontaneous, and endothermic processes. The synthesized ZnO/GPBC and GPBC are excellent adsorbents recommended for large-scale production in the removal of anionic dyes from wastewaters.

Mô hình hấp phụ đẳng nhiệt và động học hấp phụ phosphat trên vật liệu hydrotalcit Mg-Al/CO3

In this paper, the hydrotalcite Mg-Al/CO3 material was synthesized successfully with an Mg/Al molar ratio of 2:1 by the co-precipitation method. SEM images, XRD patterns and FTIR Spectra and Energy Dispersive X-ray Spectra (EDX) of the material were analyzed. Equilibrium adsorption isotherms and kinetic models of the phosphate adsorption process on the hydrotalcite material Mg-Al/CO3 were investigated. The experimental data were analyzed by Langmuir and Freundlich models of adsorption. The phosphate adsorption on the material was well fitted to both Langmuir and Freundlich isotherms, and the maximum adsorption capacity was found to be 46.95 mg/g with the material sample was calcined at 600oC. The kinetic data obtained at different concentrations have been analyzed using a pseudo-first-order and a pseudo-second-order equation. The experimental data fitted very well with the pseudo-second-order kinetic model.

The effect of Fe–Zn mole ratio (2:1) bimetallic nanoparticles supported by hydroxyethyl cellulose/graphene oxide for high-efficiency removal of doxycycline

In this research, Hydroxyethyl cellulose – graphene oxide HEC-GO and HEC-GO/Fe–Zn mole ratio (2:1) nanocomposite as adsorbents were fabricated by crosslinking ethylene glycol dimethacrylate (EGDMA) to study the thermodynamic, kinetic and isotherm of doxycycline antibiotic adsorption. The morphology and structure of the adsorbents were analyzed by Fourier transform infrared spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (FE-SEM- EDX), and Transmission electron microscopy (TEM). The adsorption behavior of doxycycline (DOX) was studied with different parameters including doxycycline concentration, pH, the dose of adsorbent (HEC-GO and HEC-GO/Fe–Zn, mole ratio (2:1)), contact time, and temperature. The optimal conditions for the removal of DOX are pH = 3.0, contact time 100 min, and 20 min for HEC-GO and HEC-GO/Fe–Zn mole ratio (2:1). The removal percentage for HEC-GO and HEC-GO/Fe–Zn mole ratio (2:1) was 97% and 95.5%, respectively. Equilibrium adsorption isotherms such as the Langmuir, Freundlich, and Temkin models were analyzed according to the experimental data. Also, four adsorption kinetics were investigated for removing DOX. The Langmuir isotherm and pseudo-second-order kinetic models provided the best fit for experimental data for HEC-GO and HEC-GO/Fe–Zn mole ratio (2:1). Thermodynamic data showed that negative values of Gibbs free energy (ΔG°) and the negative value of enthalpy (ΔH°) of the adsorption process for adsorbents. It means that DOX removal was a spontaneous and exothermic reaction.

Synthesis and characterization of montmorillonite – Mixed metal oxide composite and its adsorption performance for anionic and cationic dyes removal

Composite material based on montmorillonite – mixed metal oxides (MMT_MMO) derived from ZnAl layered double hydroxides was successfully synthesized by facile co-precipitation method under the presence of montmorillonite suspension followed by calcination at 400 °C. The as-synthesized material was characterized by several characterization techniques, including XRD, FTIR, SEM, TEM, TGA, and BET, then tested as an adsorbent for removal of both methylene blue (MB) as a cationic dye and congo red (CR) as the anionic dye from aqueous solution under different contact time, dye concentration, temperature, and pH. The as-synthesized MMT_MMO exhibited the hybrid characteristic of MMT and nano-sized mixed metal oxides. Nano-sized mixed metal oxides were successfully distributed on the surface of MMT, which brings advantages to improving the adsorption capacity of the material for anionic-based dye removal. Moreover, the average pore diameter of synthesized MMT_MMO composite was not significantly different (3.69 nm) compared to the original MMT (3.70 nm). The adsorption kinetics of MB and CR onto MMT_MMO was best fitted by the pseudo-second-order model, which indicated that the rate-limiting step was chemisorption. The equilibrium adsorption isotherm modeling to the experimental data revealed that the adsorption equilibrium data were best fitted by the Langmuir model, with maximum adsorption capacity reached 40 mg/g, which indicated that the sorption process occurred chemically in a monolayer of a homogenous surface. The calculation of the adsorption thermodynamic parameters exhibited that the adsorption process was conducted spontaneously under endothermic nature. This work provides a facile method for producing bifunctional material for the adsorption of both anionic and cationic dyes, which exhibited potential for total dyes removal from industrial wastewater.

Interfacial behavior of vegetable protein isolates at sunflower oil/water interface

Proteins are widely used in the formation and stabilization of multiphase systems, thanks to their ability to adsorb at the interface reducing the interfacial tension and promoting the formation of viscoelastic layers. Owing to the growing consumer demand, the food industry is moving toward the growing use of plant-based proteins, suitable for consumers who do not eat products of animal origin, for either ethical or health reasons. Nevertheless, the scientific literature lacks information on the surface activity and emulsifying ability of these proteins. In this work, the interfacial properties of soy, hemp and brown rice isolate proteins were investigated at the interface with commercial sunflower oil (O/W) to evaluate their characteristics in view of potential uses in food applications such as emulsions, sauces, dressing, topping and soft foods. Dilatational and shear kinematic, with pendant drop and magnetic rod techniques, respectively, were used. The dilatational analysis was performed in static and dynamic conditions, to obtain the equilibrium adsorption isotherms and the rheological parameters of the interfacial layers under both oscillation and stress relaxation. The interfaces were studied in shear conditions with small amplitude oscillations and creep tests. The obtained results evidenced that all tested proteins are able to build a strong viscoelastic layer with properties comparable to those of animal proteins. Brown rice protein seems particularly effective in reducing the interfacial tension even if shear tests evidence that the interface is weaker than that obtained using hemp or soy protein. Hemp protein seems very promising for potential practical uses yielding intermediate interfacial tensions and strong viscoelastic layers.

Removal of As(III)/As(V) from aqueous solution using newly developed thiosalicylic acid coated magnetite [TSA@Fe3O4] nanoparticles.

The aim of this study was to develop an affordable adsorption methodology for removal of As(III)/As(V) from contaminated water. Herein, novel adsorbent TSA@Fe3O4 nanoparticles (NPs) were synthesized by decorating thiosalicylic acid (TSA) on magnetite nanoparticles (Fe3O4 NPs) and employed for removal of As(III)/As(V) species from artificially contaminated natural water systems. TSA@Fe3O4 NPs demonstrated excellent adsorption efficiency (AE) and 98% of As(V) and 93% of As(III) was removed at optimized experimental conditions. The adsorption kinetic and equilibrium isotherm studies were conducted preferentially for As(III) adsorption. Adsorption followed the pseudo-second-order kinetic (R2 = 99%) and adsorption data fitted well in Langmuir isotherm model (R2 = 99%) and maximum adsorption capacity (Qmax = 34.1mg/g) was calculated for 5mg/L of As(III) by using 10mg of TSA@Fe3O4 NPs. The effect of pH, contact time, adsorption dosages, and competitive anions was also examined to identify optimum experimental conditions. The adsorbent was characterized by advanced instrumental techniques to investigate the physicochemical properties and stability of NPs. To comprehend the interactions of As(III) species with adsorbent NPs, NPs were analyzed using XPS and Raman spectroscopy techniques. Both the techniques confirmed that As(III) and As(V) species present simultaneously on adsorbent surface. The TSA@Fe3O4 was regenerated using 0.1M NaOH. The findings of this study suggested that TSA@Fe3O4 NPs could be considered a potential adsorbent for effective remediation of As(III) and As(V) from contaminated natural water systems.

Separation of nadolol racemates by high pH reversed-phase fixed-bed and simulated moving bed chromatography

The separation of nadolol racemates under high pH reversed-phase using both the fixed-bed (FB) and the simulated moving bed (SMB) preparative chromatographic techniques is reported after the previous published work [1] where the Waters XBridge C18 adsorbent and an ethanol:water:diethylamine solvent mixture were validated to allow the separation of the multicomponent feed mixture composed by four nadolol stereoisomers into two pure racemates (two pairs of enantiomers).In this work, the experimental preparative separations using one commercial fixed-bed preparative HPLC Azura system equipped with one sole column of preparative dimensions (30 mm ID × 250 mm L) and one lab-scale SMB apparatus (the FlexSMB-LSRE pilot unit) equipped with six semi-preparative columns (19 mm ID × 100 mm L) are presented. Both systems use the Waters XBridge C18 adsorbent of 10 μm particle diameter. The screening of the mobile phase composition elected the 30:70:0.1 (v/v/v) ethanol:water:diethylamine solvent mixture to perform both FB and SMB preparative operations.A large set of experimental, modelling and simulation results are presented, including pulses, measurement and modelling of the adsorption equilibrium isotherms, and its validation through breakthroughs measurements. The modelling and simulation steps allowed the prediction and the optimization of both the FB and SMB operating conditions.For FB, using a feed concentration of 9 g/L of an equimolar mixture of the two nadolol racemates, both were recovered almost pure (at least 99.9 %), with a global system productivity of 3.06 gfeed/(Lbed.hr) and a solvent consumption of 4.21 Lsolvent/gfeed. For SMB, the pilot unit’s pressure drops limits imposed a maximum internal flow-rate of only 5 mL/min and, for a nadolol feed concentration of 2 g/L, both racemates were recovered 100 % pure, with a system productivity of 0.13 gfeed/(Lbed.hr) and a solvent consumption of 6.19 Lsolvent/gfeed. Additional simulation results showed that a SMB preparative unit can perform the 9 g/L nadolol racemate separation with a system productivity of 3.61 gfeed/(Lbed.hr) and a solvent consumption of only 1.95 Lsolvent/gfeed using the same average internal flow-rate as in FB operation. Even better SMB productivities can still be obtained using the same feed or solvent flow-rates as in FB operation if the internal SMB flow-rates are allowed and not limited by the system pressure drop.The experimental results presented in this work validate the strategy of separating a four nadolol stereoisomers mixture into two pure nadolol racemates, each one composed by a pair of nadolol enantiomers, using an achiral C18 adsorbent through FB and SMB chromatographic techniques. Each nadolol racemate can later be purified into pure nadolol stereoisomers using standard binary chiral FB and SMB chromatography. In this way, this works introduces a real and experimental solution for the complete multicomponent preparative separation of the four nadolol stereoisomers.

Insight into the molecular interaction of trace As (III) and As(V) onto the hybrid anion exchanger impregnated with Fe/Mn nanoparticles (HA502P-Fe/Mn)

In this study, a hybrid anion exchanger impregnated with Fe/Mn nanoparticles (HA502P-Fe/Mn) was synthesized via two-step mixed metal oxide precipitation using 50:50 % DI: ethanol as solvent. Trace As(III) and As(V) removal efficiency was comprehensively validated in both equilibrium adsorption isotherms and kinetics. The maximum adsorption capacities of HA502P-Fe/Mn toward As(III) and As(V) were 21,590 and 18,930 µg/g, respectively. The kinetics of As(III) removal were best predicted (R2 = 0.986) using a pseudo-second order model (k2 = 0.001 g/µg As(III)·min). Adsorption mechanisms were further characterized using X-ray absorption spectroscopy (XANES and EXAFS), including a comparison with the density functional theory (DFT) data. The XANES results showed complex redox transformation of the adsorbed As(V) on HA502P-Fe/Mn. The EXAFS spectra indicate predominant inner-sphere complex formation of bidentate mononuclear edge-sharing (2E) complexes for Mn-As (bond distance 2.94 Å), and bidentate binuclear corner-sharing (2C) complexes for Fe-As (bond distance 3.34 Å) on HA502P-Fe/Mn surfaces. Based on the DFT simulation, the obtained 3D structures were optimized, and the bond lengths between Fe-As and Mn-As were comparable with the EXAFS. For practical purposes, the fixed-bed column experiments were fully investigated for both As(III) and As(V) removal using NSF standard 53 test water (As(III) 300 ppb, pH 6.5), including the regeneration. The HA502P-Fe/Mn demonstrated 2X treatable bed volumes (4,300 vs 2,000 BVs) more than the commercially available As selective adsorbent. The experiments demonstrated that HA502P-Fe/Mn is a promising novel adsorbent for As(III) removal owing to its relatively high As adsorption capacity and regenerating ability.

Porous material based on modified carbon and the effect of pore size distribution on the adsorption of methylene blue dye from an aqueous solution.

Carbon porous materials obtained through KOH activation of a furfural + hydroquinone + urotropine mixture were applied as adsorbent for the remediation of methylene blue (MB). The impact of porous structure with special attention to pore size distribution along with well-known pore volume and specific surface area on the remediation of MB was well investigated and elucidated. Findings obtained revealed that pore size distribution plays a crucial role in the liquid-phase adsorption of organic dyes like MB. By varying the synthesis mode parameters, in particular, the activating agent/precursor mass ratio, with the composition and initial components ratios remaining unchanged, samples with different pore size distribution were obtained. It was found that the material predominantly containing pores with an average equivalent diameter of ~ 3.5nm appears to be the efficient MB adsorbent. The resulting highly porous carbon materials demonstrated high MB adsorption capacity (up to 2555mg/g). Furthermore, to fully elucidate the adsorption mechanisms occurring on the obtained materials, a comprehensive mathematical processing of experimental data was performed out using the known kinetic and diffusion models (pseudo-first- and pseudo-second order, and intraparticle diffusion), as well as adsorption equilibrium isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich).It can be concluded that the porous carbon materials obtained and described in the present work are effective adsorbents for the removal of MB and may possess great potential for the treatment of dye-containing wastewater.

4-picoline adsorption from aqueous solution by using baggage fly ash (BFA): Parametric, kinetic and thermodynamic aspects

Abstract Numerous harmful characteristics of wastewater containing pyridine chemical have a significant negative impact on human health. Therefore, it is preferred to remove it from effluent. The derivatives of pyridine are 2- and 4-picoline. In this work, an adsorption technique was used to remove 4-picoline from the effluent. Wastewater was treated to remove 4-picoline using the natural adsorbent baggage fly ash (BFA). 4-picoline adsorption rate of 82% was reported at pH 6.22, BFA adsorbent dosage of 4 g/L, and contact time of 6 h. The current investigation found that 85.83% of 4-picoline could be removed at its maximum with BFA at a temperature of 333 K. Investigations were also carried out into how the starting concentration and temperature affected the elimination of 4-picoline. According to the kinetic analysis, the process uses pseudo-second-order rate kinetics. The thermodynamics study also demonstrated that all temperatures could be predicted using the Freundlich and Langmuir equilibrium adsorption isotherm models. It further demonstrated that 4-picoline adsorption on BFA is an endothermic process.

Selective adsorption and separation of light hydrocarbon gases in VI/IV dipeptide crystals

The separation of propane/propylene mixtures remains a subject under intensive research because designing cheaper, greener and sustainable processes is of paramount importance to industry. Dipeptides crystallize into several lattices displaying a variety of porosities that enable the separation of species with approximate size. In this study, we show that microporous crystals of L-Isoleucyl–l-Valine (IV) and L-Valyl-l-Isoleucine (VI) are able to distinguish between methane, propane and propylene. Adsorption equilibrium isotherms were determined and coupled with Molecular Dynamics simulations for computing diffusion and loading of binary mixtures of relevant gases in the dipeptide frameworks to obtain kinetic and equilibrium gas mixtures selectivities. It was found that although the pore diameters in both dipeptide crystals are similar, VI has a higher permselective separation of propane/propylene mixtures displaying a maximum ideal permselectivity of αP(C3H6)/C3/H8) = 1.3.

Magnetite-silica core–shell grafted myristic acid nanocomposites for oil adsorption from petroleum wastewater

Removing oil content from this water is critical for meeting governmental discharge limitations and providing a large amount of clean water. In this study, a new magnetite-silica core/shell nanocomposite was synthesized and functionalized with myristic acid and designated by (Fe3O4/SiO2@MA) used to remove oil from petroleum wastewater. Various analytical techniques characterize the prepared nanocomposite, such as XRD, FTIR, TEM, and SEM. The adsorption experiments were carried out in batch mode to determine the effect of the pH, amount of adsorbent, initial concentration of the emulsified oil, temperature, and contact time. The results indicate that the adequate conditions to adsorb emulsified oil onto (Fe3O4/SiO2@MA) were at pH 10, at 60 °C, emulsified oil concentration of 0.5 g/L during one h of contact time. Finally, the results showed that 1 g of (Fe3O4/SiO2 @ MA) can absorb 81.4% of emulsified oil. The Langmuir and Freundlich models were used to describe the adsorption isotherm equilibrium. The adsorption isotherm was best fitted well with the Langmuir model. The kinetic evaluations of oil removal by the Fe3O4/SiO2@MA followed pseudo-second-order.

On As(III) Adsorption Characteristics of Innovative Magnetite Graphene Oxide Chitosan Microsphere.

A magnetite graphene oxide chitosan (MGOCS) composite microsphere was specifically prepared to efficiently adsorb As(III) from aqueous solutions. The characterization analysis of BET, XRD, VSM, TG, FTIR, XPS, and SEM-EDS was used to identify the characteristics and adsorption mechanism. Batch experiments were carried out to determine the effects of the operational parameters and to evaluate the adsorption kinetic and equilibrium isotherm. The results show that the MGOCS composite microsphere with a particle size of about 1.5 mm can be prepared by a straightforward method of dropping FeCl2, graphene oxide (GO), and chitosan (CS) mixtures into NaOH solutions and then drying the mixed solutions at 45 °C. The produced MGOCS had a strong thermal stability with a mass loss of <30% below 620 °C. The specific surface area and saturation magnetization of the produced MGOCS was 66.85 m2/g and 24.35 emu/g, respectively. The As(III) adsorption capacity (Qe) and removal efficiency (Re) was only 0.25 mg/g and 5.81% for GOCS, respectively. After 0.08 mol of Fe3O4 modification, more than 53% of As(III) was efficiently removed by the formed MGOCS from aqueous solutions over a wide pH range of 5–10, and this was almost unaffected by temperature. The coexisting ion of PO43− decreased Qe from 3.81 mg/g to 1.32 mg/g, but Mn2+ increased Qe from 3.50 mg/g to 4.19 mg/g. The As(III) adsorption fitted the best to the pseudo-second-order kinetic model, and the maximum Qe was 20.72 mg/g as fitted by the Sips model. After four times regeneration, the Re value of As(III) slightly decreased from 76.2% to 73.8%, and no secondary pollution of Fe happened. Chemisorption is the major mechanism for As(III) adsorption, and As(III) was adsorbed on the surface and interior of the MGOCS, while the adsorbed As(III) was partially oxidized to As(V) accompanied by the reduction of Fe(III) to Fe(II). The produced As(V) was further adsorbed through ligand exchange (by forming Fe–O–As complexes) and electrostatic attraction, enhancing the As(III) removal. As an easily prepared and environmental-friendly composite, MGOCS not only greatly adsorbs As(III) but also effectively removes Cr(VI) and As(V) (Re > 60%) and other metals, showing a great advantage in the treatment of heavy metal-contaminated water.